From 320d25b6a05f8b73c23fc21025d2906ecdd2d4fc Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 19 Jan 2016 13:38:58 -0800 Subject: [PATCH] x86/mm/32: Set NX in __supported_pte_mask before enabling paging There's a short window in which very early mappings can end up with NX clear because they are created before we've noticed that we have NX. It turns out that we detect NX very early, so there's no need to defer __supported_pte_mask setup. Signed-off-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Mike Galbraith Cc: Pavel Machek Cc: Peter Zijlstra Cc: Stephen Smalley Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/2b544627345f7110160545a3f47031eb45c3ad4f.1453239349.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/head_32.S | 6 ++++++ arch/x86/mm/setup_nx.c | 5 ++--- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 6bc9ae24b6d2..57fc3f8c85fd 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -389,6 +389,12 @@ default_entry: /* Make changes effective */ wrmsr + /* + * And make sure that all the mappings we set up have NX set from + * the beginning. + */ + orl $(1 << (_PAGE_BIT_NX - 32)), pa(__supported_pte_mask + 4) + enable_paging: /* diff --git a/arch/x86/mm/setup_nx.c b/arch/x86/mm/setup_nx.c index 92e2eacb3321..78f5d5907f98 100644 --- a/arch/x86/mm/setup_nx.c +++ b/arch/x86/mm/setup_nx.c @@ -31,9 +31,8 @@ early_param("noexec", noexec_setup); void x86_configure_nx(void) { - if (boot_cpu_has(X86_FEATURE_NX) && !disable_nx) - __supported_pte_mask |= _PAGE_NX; - else + /* If disable_nx is set, clear NX on all new mappings going forward. */ + if (disable_nx) __supported_pte_mask &= ~_PAGE_NX; } -- 2.30.2